1. Field of the Invention
The present invention relates to a speech processing apparatus which performs speech recognition or speech synthesis and a control method for the apparatus.
2. Description of the Related Art
Recently, a speech recognition technique of controlling a device with speech has been put into practice. The speech recognition technique has a great advantage of allowing users such as children, elderly people, and physically handicapped people to control devices by speech utterance. Such a speech recognition technique has been particularly commercialized in the fields of car navigation systems, telephone services, welfare equipment, and the like.
In general, when a device is to be controlled by speech recognition, speech from the user is captured through a microphone as a speech input device built in the device. Some users, however, may use their own microphones. When using speech recognition in operator work such as telephone operation, the operator often uses his/her own headset microphone in consideration of hygiene. In addition, a physically handicapped user uses a microphone conforming to his/her own physical handicap.
When a user uses speech recognition through his/her own microphone, the device compatible with speech recognition needs to have a terminal into which the user's microphone can be plugged. Some apparatuses compatible with speech recognition have such microphone terminals.
Assume that an apparatus compatible with speech recognition has a terminal which allows connection of a user's microphone. In this case, the user can connect the microphone to the terminal during speech recognition. Electrical noise tends to occur at the time of connection of the microphone. Such noise is captured as speech noise by a speech recognition apparatus. If the apparatus erroneously recognizes such speech noise as some utterance from the user, the device may execute a command which the user does not desire.
Japanese Patent Laid-Open No. 62-150295 discloses a technique of suspending speech recognition when the intensity of noise input from a microphone is equal to or more than a predetermined level.
However, the characteristic of electrical noise caused at the time of insertion/removal of the microphone often affects speech recognition more than the intensity of the noise. It is therefore inappropriate to suspend speech recognition processing based only on the intensity of the noise as a decision criterion.
In addition, a microphone built in a device and a microphone which the user connects may differ in the optimal values of internal parameters used for speech recognition. For example, the optimal value of a speech input volume in the microphone built into the device might degrade the recognition performance based on the microphone which the user connects.
There has been no prior art giving consideration to the connection/disconnection of a microphone at the time of speech recognition.